The present invention relates to intraocular lenses (IOLs). More particularly, the present invention relates to IOLs which are adapted to provide accommodating movement in the eye.
The human visual system includes the eyes, the extraocular muscles which control eye position within the eye socket, the optic and other nerves that connect the eyes to the brain, and particular areas of the brain that are in neural communication with the eyes. The visual system is particularly well adapted for the rapid and precise extraction of spatial information from a field of view, by analyzing the continuously changing patterns of radiant flux impinging upon the surfaces of the eyes.
Image formation is greatly complicated by the movement of the eyes within the head, as well as by the movement of both eyes and the head relative to the external sea of radiant energy. Visual input is ordinarily sampled by discrete momentary pauses of the eyes called fixations, interrupted by very rapid ballistic motions known as saccades which bring the eye from one fixation position to the next. Smooth movements of the eyes can occur when viewing an object having a predictable motion.
Each eye forms an image upon a vast array of light sensitive photoreceptors of the retina. The outer cover of the eye, or cornea, protects the lens and acts as a colorless filter to refract light onto the iris and pupil. The iris corresponds to the aperture in a camera and contains muscles which alter the size of the pupil to control the amount of light that enters the eye. The crystalline lens located just behind or posterior to the pupil has a variable shape under the indirect control of the peripheral ciliary muscles. Having a refractive index higher than the surrounding media, the crystalline lens gives the eye a variable focal length, allowing accommodation to objects at varying distances from the eye.
Much of the remainder of the eye is filled with fluids and materials under pressure which help the eye maintain its shape. For example, the aqueous humor fills the anterior chamber between the cornea and the iris, and the vitreous humor fills the majority of the volume of the eye in the vitreous chamber located between the lens and the retina. The crystalline lens is contained within a third chamber of the eye, the posterior chamber, which is positioned between the anterior and vitreous chambers.
The human eye is susceptible to numerous disorders and diseases, a number of which attack the crystalline lens. For example, cataracts mar vision through cloudy or opaque discoloration of the lens of the eye. Cataracts often result in partial or complete blindness. If this is the case, the crystalline lens can be removed and replaced with an intraocular lens, or IOL.
While restoring vision, conventional monofocal IOLs have only limited or substantially no ability for accommodation (i.e., the focusing on near objects). To overcome this lack of accommodation, a patient may be prescribed eyeglasses. Alternative attempts in the art involve enhancing the accommodation ability of IOLs. Accommodation may be accomplished by either changing the shape of the IOL, e.g., to become more convex for near vision focus, or by moving the IOL along its optical axis. For example, a number of these approaches bias an IOL to be located in the most posterior position of the posterior capsular bag of the eye under rest conditions. When near focus is required, the IOL moves forwardly in response to the action of the ciliary muscle of the eye to provide positive accommodation. These approaches often result in insufficient forward axial movement required for full-range accommodation.
In view of the foregoing, it would be beneficial in the art to provide IOLs with enhanced capacity for accommodation.
The present invention provides new and enhanced holders for intraocular lenses (IOLs) to enhance accommodation of one or more IOLs. Desirably, the holders of the invention also inhibit cell growth, particularly epithelial cell growth, onto the IOL or IOLs retained thereby. The holders of the present invention are straightforward in design and construction, thereby facilitating the manufacturing process, and produce substantial benefits in use in the eye.
According to one aspect of the invention, a holder for an intraocular lens has a holder body that is sized and adapted to be placed in a capsular bag of an eye. The holder body defines a hollow space adapted to receive and retain a fixation member of an IOL. The holder is configured to enhance the accommodation of the IOL in response to contraction and relaxation of the ciliary muscle of the eye. The holder body may be configured to be either separate and apart from the IOL or permanently coupled to the IOL.
According to one useful embodiment of the present invention, the holder body is made from a resilient or compressible material such that the holder body is adapted to cooperate with the eye to facilitate accommodating movement of the intraocular lens. For example, in one embodiment, when the ciliary muscle contracts, the zonules relax and reduce the equatorial diameter of the capsular bag, thereby compressing the holder body and moving the lens therein anteriorly along the optical axis of the eye. This anterior movement of the lens increases or amplifies the amount of positive (i.e., near) accommodation of the lens. Conversely, when the ciliary muscle relaxes, the zonules constrict and increase the equatorial diameter of the capsular bag, thereby allowing the holder body to expand and return to an unstressed shape, which moves the lens posteriorly along the optical axis.
The holder body of the invention may take on a number of specific configurations. For example, the holder body may be circular and shaped like a tire with a peripheral wall and a pair of opposing side walls together defining an annular channel therewithin. Alternatively, the holder body may be C shaped. To enhance collapsibility when the equatorial diameter of the capsular bag is reduced, for example, when the ciliary muscle contracts, the holder body may include a plurality of voids, such as notches formed in the opposing side walls.
One of advantages of the invention results from particularly-shaped annular intersections between the peripheral wall and the pair of opposing side walls. More specifically, to inhibit cell growth along onto the lens, the intersections between the peripheral wall of the holder body and the side walls are substantially discontinuous. For example, the side walls may be disposed substantially perpendicularly to the peripheral wall. Alternatively, the side walls may angulate outwardly from the peripheral wall, e.g., at an angle of up to about 45xc2x0. In either embodiment, the peripheral intersection may be considered sharp or abrupt and is effective in inhibiting migration or growth of cells from the eye onto the IOL.
The present invention also provides holders for retaining more than one IOL. According to this aspect of the present invention, the holder body defines an additional hollow space adapted to receive and retain a distal end portion of an additional fixation member of second intraocular lens. Preferably, the holder body includes a spacer member adapted to maintain the fixation member of the first IOL spaced apart from the fixation member of the second IOL.
In one of the useful embodiments of the multi-IOL holders of the invention, an annular ring is disposed in one of the hollow spaces. Accordingly, the inner diameter of one of the hollow spaces is less than that of the other hollow space. Accordingly, the present holders may hold and retain IOLs of different size. In addition, the multi-IOL holder body is adapted to cooperate with the eye to facilitate accommodating movement of at least one of the intraocular lens retained thereby.
One of the advantages of the retaining lenses of different size is that the holder of the present invention is able to compensate for capsule size variations and to shift the axial position of a dynamic accommodating lens. By shifting the axial position of the dynamic accommodating lens, axial movement is maximized, and hyperopic refractive errors are avoided. The annular ring may also be used to correct axial position errors in either the one-lens or the two-lens system.
Any and all of the features described herein and combinations of such features are included within the scope of the present invention provided that the features of any such combination are not mutually inconsistent.
Additional aspects, features, and advantages of the present invention are set forth in the following description and claims, particularly when considered in conjunction with the accompanying drawings in which like parts bear like reference numbers.